CVE-2018-25235: NetworkActiv Web Server DoS Vulnerability

CVE-2018-25235 Overview

NetworkActiv Web Server 4.0 contains a buffer overflow vulnerability (CWE-787: Out-of-Bounds Write) in the username field of the Security options that allows local attackers to crash the application by supplying an excessively long string. Attackers can trigger a denial of service by entering a crafted username value exceeding the expected buffer size through the Set username interface.

Critical Impact

Local attackers can cause a complete denial of service by crashing the NetworkActiv Web Server application through a buffer overflow in the username configuration field.

Affected Products

• NetworkActiv Web Server 4.0

Discovery Timeline

• 2026-03-30 - CVE-2018-25235 published to NVD
• 2026-03-30 - Last updated in NVD database

Technical Details for CVE-2018-25235

Vulnerability Analysis

This vulnerability stems from improper input validation in the Security options interface of NetworkActiv Web Server 4.0. The application fails to properly validate the length of user-supplied input in the username field, allowing attackers to provide an excessively long string that overwrites adjacent memory. This out-of-bounds write condition corrupts memory structures critical to application stability, resulting in an application crash. The vulnerability requires local access to exploit, meaning an attacker would need to interact with the application's Security configuration interface directly.

Root Cause

The root cause is a classic buffer overflow condition (CWE-787) where the application allocates a fixed-size buffer for the username field but does not enforce proper bounds checking on user input. When a string exceeding the expected buffer size is entered, the application writes beyond the allocated memory boundary, leading to memory corruption and subsequent application failure.

Attack Vector

The attack requires local access to the NetworkActiv Web Server application's Security options interface. An attacker with access to the configuration panel can navigate to the username field settings and enter an excessively long string. The vulnerability is triggered when the application attempts to process this oversized input without proper length validation, causing a buffer overflow that crashes the server process.

The exploitation mechanism involves crafting a username string that exceeds the expected buffer allocation. When submitted through the Set username interface, the oversized input overwrites adjacent memory regions, corrupting application state and triggering a crash. Technical details and proof-of-concept information are available through the Exploit-DB #45302 entry and the VulnCheck Advisory on NetworkActiv.

Detection Methods for CVE-2018-25235

Indicators of Compromise

• Unexpected crashes of the NetworkActiv Web Server application, particularly following configuration changes
• Crash logs or dump files indicating memory access violations in the Security options component
• Evidence of abnormally long strings in configuration files or recent user input logs
• Application event logs showing unhandled exceptions during username field processing

Detection Strategies

• Monitor for NetworkActiv Web Server process crashes and restart patterns
• Implement application-level logging to capture unusual input lengths in configuration fields
• Use endpoint detection and response (EDR) solutions to detect buffer overflow exploitation attempts
• Monitor Windows Event Logs for application crash events related to NetworkActivWebServer.exe

Monitoring Recommendations

• Configure SentinelOne agents to monitor the NetworkActiv Web Server process for suspicious behavior and crash events
• Set up alerting for repeated application crashes that may indicate exploitation attempts
• Implement file integrity monitoring on NetworkActiv Web Server configuration files
• Review system logs regularly for signs of denial of service conditions

How to Mitigate CVE-2018-25235

Immediate Actions Required

• Restrict local access to the NetworkActiv Web Server configuration interface to authorized administrators only
• Implement strong access controls on systems running NetworkActiv Web Server 4.0
• Consider deploying application control policies to limit who can modify server configurations
• Evaluate whether NetworkActiv Web Server is essential to operations and consider alternative web server solutions if possible

Patch Information

No official patch information is currently available in the CVE data. Administrators should monitor the Network Activ Development Page and Network Activ Web Server Info for updates from the vendor. The VulnCheck Advisory on NetworkActiv may also provide updated remediation guidance.

Workarounds

• Limit physical and remote access to systems running NetworkActiv Web Server to trusted personnel only
• Configure the username field with a valid value before restricting access to the Security options interface
• Implement network segmentation to isolate systems running NetworkActiv Web Server from untrusted users
• Consider deploying a web application firewall or reverse proxy in front of NetworkActiv Web Server to add an additional security layer

Administrators should apply the principle of least privilege to all accounts with access to the NetworkActiv Web Server configuration, ensuring only essential personnel can modify security settings.